1. Field of the Invention
The present invention relates to an active matrix display device, and more particularly to an active-type display device that executes signal write using a current signal.
2. Description of the Related Art
Thee has been an increasing demand for a flat-panel display device that is typified by a liquid crystal display device, which has advantageous features of small thickness, light weight and low power consumption, compared to a CRT display. In particular, an active matrix display device, in which each pixel is provided with a switch that has a function of electrically separating an on-pixel and an off-pixel and holding a video signal to the on-pixel, is capable of achieving a good display quality without crosstalk between adjacent pixels. Thus, the active matrix display device has recently been applied to various displays including displays of mobile information devices.
In the field of liquid crystal displays, there is known a technique wherein a driver circuit that outputs video signals to pixels is formed of semiconductor devices using polysilicon and is integrally built on the same substrate as pixels. Thereby, the number of contacts between the panel and external circuits can be reduced, and the mechanical strength of the display device can be increased.
In recent years, organic electroluminescent (EL) display devices have widely been developed as self-luminous displays that can achieve higher responsivity and a wider viewing angle than liquid crystal displays. For instance, a technique of integrally forming a driver circuit on the same substrate as pixels in the field of organic EL displays is discussed in Reiji Hattori, et al. (three), “Circuit Simulation of Polysilicon TFT Based Current-Writing Active-Matrix Organic LED Display”, IEICE Technical Report, the Institute of Electronics, Information and Communication Engineers (IEICE), 2001, Vol. 101, No. 15, pp. 7–14.
In the case of integrally forming a driver circuit on the same substrate as pixels, however, a display defect tends to occur due to non-uniform characteristics of semiconductor devices that are formed of polysilicon.